I noticed you referenced my website in your PDF but clearly failed to even skim the 380-page PhD living there which contradicts almost everything you’ve asserted.

What urban explorers are doing by sneaking into places is expressing deep admiration for their environment and its history. They are participatory citizens who take an active interest in their city and inspire others to playfully and creatively engage with their surroundings. They also have a strong sense of community, the very thing that makes a city safer.

Countless historical precedents show that when and if terrorists strike, they will do so pretty much out in the open, aiming to inflict maximum human casualties – an attack is as much psychological as physical. Let’s take a metro tunnel as an example, which you suggest could be targeting for “disruption of service because of access to electrical, ventilation, or signal control rooms.” Why would you study urban explorer’s photos to find a way to abseil down a ventilation shaft into an abandoned tube station to disrupt a signal? This would be incredibly time-consuming, difficult and not very effective, especially when you can walk into a train with a valid ticket and an organic peroxide–based device in a rucksack. You may remember this happened in here in the UK on the 7th July 2005 that killed 52 people.

You know what your best defence against terrorism is? A bunch of people who love their city, paying attention, with cameras. That’s a perfect description of urban explorers.
McCarthyism is the practice of making accusations of disloyalty, subversion, or treason without proper regard for evidence. That is what you are propagating here. I think it might be worth taking the time to consider who is doing the “terrorising”. Using a vague threat to limit people’s right to spend their free time as they wish is unwarranted, unethical and authoritarian. Just to be clear: it’s drivel like this that is destroying the last vestiges of democracy.

It’s worth considering this passage from 2003 by the explorer couple Liz and Ninjalicious which still resonates strongly today, especially in the context of your naïve overzealousness:
“Allowing the darkening threat of future terrorist attack or indeed of our increasingly scarce civil rights to deter our curiosity or intimidate us away from expressing our deep appreciation for the hidden and neglected bits of our urban landscapes would be the greatest crime of all. Continuing to support considerate exploration and questioning authority in productive, benevolent, and visible ways will allow us to represent ourselves as what we really are: people who love our cities, not those who wish to destroy them.”